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Citation. Tilman, D. 1989. Competition, nutrient reduction, and the competitive neighborhood of a bunchgrass. Functional Ecology 3:215-219. [1170 LTER]
Abstract. The bunchgrass, Schizachyrium scoparium (Michx.) Nash-Gould, is often the dominant species on unproductive, nitrogen-poor, sandy soils in Minnesota. Removal of all neighbouring plant biomass within a 2 m radius of individual Schizachyrium scoparium bunches resulted in a 3 8-fold increase in the biomass of S. scoparium bunches and demonstrated that the neighbouring plants had been reducing the level of extractable ammonium plus nitrate by 3 9-fold. Contrary to Grime's (1979) assertion, this suggests that there may be strong competition in this unproductive habitat. The mechanism of competition may be nutrient consumption. Schizachyrium scoparium significantly reduced nitrate and ammonium levels within a 60-75 cm radius around individual plants, with the magnitude of reduction decreasing with distance from an individual. The neighbourhood from which a S. scoparium bunch obtains nitrogen thus had an area of 1-1.5 m2 and may include hundreds of other individual plants.
Keywords. Schizachyrium scoparium, nutrient reduction, neighbourhood competition, nitrate, ammonium, competition for nitrogen